1. Field of the Invention
The invention relates to a headrest device for an active headrest for protecting a person at the time of impact (at the time of collision), and particularly, relates to a headrest device for an active headrest, which is capable of achieving protection of a person's head and neck and upward movement (ascent) and forward tilting of the headrest at high speed (or instantaneously) before ascent of the head (extension of the neck) at the time of collision, thereby achieving avoidance of whiplash, avoidance of neck injury, and the like through the protection of the head and neck.
2. Description of the Related Art
As known in the art, quality required for an automobile (vehicle) has evolved to include emission, horse power, fuel efficiency, safety, silence and ride comfort to meet demands of various kinds of people, such as passengers. Among these qualities, with a need to improve headrest performance from the standpoint of safety, for example, an active headrest has been put in practical use and inventions to support such practical use have been made. The headrest has as its requirements quick ascent and forward tilting of the headrest, accurate movement of the headrest, suppression of rattling sounds, an ensured role of the headrest at an emergency from the standpoint of frequent occurrence of accidents and/or various collisions, and the like.
The headrest meets a passenger's needs by being typically installed about 30 mm to 50 mm away from the passenger's head, without contact with the passenger's head to alleviate the passenger's unpleasant feeling. However, in actuality, such a headrest may cause an unexpected trouble at an emergency such as an impact and/or collision. An example of such a trouble is given below, including the relationship between the headrest and a seat.
In the prior art, a seat protects a passenger's back against an impact since the passenger's back contacts a seat back for the purpose of safety and/or comfortable driving. However, the above-mentioned headrest device does not protect the passenger's head, which gets away from the headrest. This is because the passenger's head vectorially moves upward at the time of collision. Thus, as the passenger's neck is extended, the passenger may suffer injuries ranging from light injury such as whiplash to a severe situation such as neck injury and/or amputation.
Under such circumstances, various techniques have been proposed to avoid whiplash and/or neck injury (protect a neck and/or a head) caused at the time of collision. The following Patent Documents may be cited as examples of these techniques. However, it can not be said that headrest devices disclosed in these documents are necessarily sufficient as headrest devices for an active headrest to protect a neck by ascending by a certain distance and forwardly tilting instantaneously.
JP-A-2005-296266 discloses a seat structure for a vehicle. This invention provides a seat for a vehicle in which the seat includes extendible/contractable side frames provided in a seat frame, a solenoid including a forward tilting mechanism provided between the side frames, and a headrest stay which can be elevated/lowered with respect to a headrest support provided in the solenoid, wherein a headrest can be tilted forward by the forward tilting mechanism and can be raised by ascent of the headrest stay. This technique of JP-A-2005-296266 intends to protect a passenger's neck and/or head by moving the upper part of the body of the passenger backward and moving the passenger's neck and/or head upward during rear-end collision through the ascent and forward tilting of the headrest.
Further, JP-A-2001-163099 discloses a seat structure for a vehicle. This invention provides a seat structure for a vehicle in which a headrest holder supporting a headrest stay ascends and tilts forward via a guide means provided in a frame, the guide means can return to its initial position by a regulating spring, and forward tilting and ascent of the guide means are regulated by a passive means such as a textile belt disposed in a seat back. This technique of JP-A-2001-163099 also intends to protect a passenger's neck and/or head, like JP-A-2005-296266.
Further, JP-A-2000-219069 discloses a seat structure for a vehicle. This invention provides a seat for a vehicle, including an upper pipe provided in a seat back frame, a pipe frame which is attached to the upper pipe and in/from which a headrest stay spliced and fixed to the upper pipe can be inserted/detached, a headrest supporting frame for forwardly tilting the pipe frame, and a pressure receiving portion provided in a frame for forwardly tilting the headrest supporting frame and the headrest. Accordingly, the seat back is raised and tilted forward by moving the headrest supporting frame and the pipe frame by pressing of the pressure receiving portion. This technique of JP-A-2000-219069 intends to further move the headrest forward in response to the movement amount of the pressure receiving portion with the backward movement of the upper half of the body of a passenger at the time of collision and further intends to achieve this series of operations with a simpler construction.
Moreover, JP-A-2000-211410 discloses a seat structure for a vehicle. This invention provides a seat for a vehicle in which a headrest supporting frame is provided at an upper end of a lever link mechanism secured to a seat back frame. The lever link mechanism is constituted by a lever rocking vertically in interlocking with a pressure receiving portion which moves by receiving a load at the time of collision, a first link interposed between the lever and the headrest supporting frame, and a second link interposed between the first link and the seat back frame. This technique of JP-A-2000-211410 intends to move the headrest supporting frame and the headrest diagonally forward and upward by increasing the movement amount of the pressure receiving portion to prevent a passenger from being damaged due to ascent of the passenger's head (to protect the passenger's neck and/or head).
JP-A-2005-296266 intends to protect the passenger's neck and/or head at the time of collision by ascent and forward tilting of the headrest. However, the technique of this JP-A-2005-296266 employs only a solenoid in which a forward tilting mechanism is provided. Therefore, this technique has room for further improvement, since it may be complicated in its structure and may not correctly operate in an emergency at the time of collision. In addition, when a surface of the seat back is lifted up, there is a possibility of occurrence of resistance against the ascent and/or forward tilting of the active headrest. In particular, there is a possibility of occurrence of a problem when the surface of the seat back has low tenacity and/or flexibility, like leather for luxury cars, synthetic leather, etc.
JP-A-2001-163099 also intends to protect the passenger's neck and/or head at the time of collision by ascent and forward tilting of the headrest. However, the technique of this JP-A-2001-163099 employs a construction in which the headrest stay is raised by a passive means such as a textile belt or the like. Therefore, in this technique, the movement distance of the ascent of the headrest is considered to be insufficient. For example, this technique has no consideration for the ascent of the passenger's head and thus has room for improvement to protect the passenger's head fully at the time of collision. A problem of a surface of the headrest is about the same as in JP-A-2005-296266.
JP-A-2000-219069 and JP-A-2000-211410 intend to protect the passenger's head fully at the time of collision by ascent of the headrest to the front. However, the techniques of these documents have room for improvements in the ascent distance and ascent speed to protect the passenger's head fully at the time of collision, through active ascent and forward tilting of the headrest. Further, when it is considered that the movement of passenger's head at the time of collision, ascent and/or descent with good response, etc., are secured, the technique of the document is not necessarily satisfactory. A problem of a surface of the headrest is about the same as JP-A-2005-296266.
However, there exists no active headrest to protect a passenger's head fully at the time of collision irrespective of body type or seating postures of the passenger. In addition, it is difficult for various conventionally improved active headrests to secure safety and relief of a passenger, comfort of traveling and driving, etc.